Are you sure about that?
Thank you, smoke detector installer man, for pointing out the obvious. This isn’t exactly the answer we were looking for, but it does help a bit. At least we know that you didn’t install it under the rug or inside of a cupboard somewhere.
Since smoke detectors last for around a decade, it’s crucial that you know when it was installed (on the ceiling), so you know when to replace it. A more logical person would write the date of when the smoke detector was put up, but then we wouldn’t have anyone to laugh at. Thank you, smoke detector installer man, for taking the hit.